Optical lens system for taking image

ABSTRACT

An optical lens system for taking image comprises: in order from the object side to the image side: an aperture stop; a first lens element with positive refractive power having a convex object-side surface, a second lens element with negative refractive power; a third lens element with positive refractive power having a concave object-side surface and a convex image-side surface; a plastic fourth lens element with negative refractive power having a concave image-side surface, the object-side and the image-side surfaces of the fourth lens element being aspheric. A focal length of the optical lens system for taking image is f, a focal length of the first lens element and the second lens element combined is f12, and they satisfy the relation: 0.98&lt;f/f12&lt;1.82.

This application is a divisional application of U.S. patent applicationSer. No. 12/346,802 which claims the benefit of the earlier filing dateof Dec. 30, 2008. Claims 1-11 of this application correspond to theprevious claims 13-23 of the U.S. patent application Ser. No.12/346,802.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical lens system for takingimage, and more particularly to a miniaturized optical lens system fortaking image used in a mobile phone camera.

2. Description of the Prior Art

In recent years, with the popularity of the mobile phone camera, theoptical lens system for taking image has become thinner and thinner, andthe electronic imaging sensor of a general digital camera is typically aCCD (Charge Coupled Device) or CMOS (Complementary Metal OxideSemiconductor) sensor. Due to advances in semiconductor manufacturing,the pixel size of sensors has been reduced continuously, andminiaturized optical lens systems for taking image have increasinglyhigher resolution. Therefore, there's increasing demand for imagequality.

A conventional mobile phone camera usually consists of three lenselements: from the object side to the image side: a first lens elementwith positive refractive power, a second lens element with negativerefractive power and a third lens element with positive refractivepower, such as the optical lens system for taking image described inU.S. Pat. No. 7,145,736.

As the pixel size of electronic imaging sensors gradually becomessmaller and smaller, the system requires higher image quality. Theconventional optical lens system comprising three lens elements cannotsatisfy the requirements of higher resolution optical lens systems.

U.S. Pat. No. 7,277,238 discloses a four-piece lens assembly, which hasa higher resolution than that of the three-piece lens assembly, however,the fourth lens element of the above patent is positive so that theprincipal point is close to the image side of the system, so the backfocal length of such a four-piece lens assembly is relatively longerthan that of a telephoto type four-piece lens assembly which has afourth lens element with negative refractive power. In addition, onlythe second lens element is negative, so it will be difficult to correctthe Petzval sum of the system, making it more difficult to control imagequality of the periphery of the image.

The present invention mitigates and/or obviates the afore-mentioneddisadvantages.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide an opticallens system for taking image comprising four lens elements to improveimage quality, and effectively reduce the volume of the optical lenssystem.

According to one aspect of the present invention, an optical lens systemfor taking image in accordance with the present invention comprises: inorder from the object side to the image side: an aperture stop; a firstlens element with positive refractive power having a convex object-sidesurface; a second lens element with negative refractive power; a thirdlens element with positive refractive power having a concave object-sidesurface and a convex image-side surface; and a fourth lens element withnegative refractive power having a concave image-side surface, thefourth lens element can be plastic, the object-side surface and theimage-side surface of the fourth lens element can be aspheric. Sucharrangements can effectively improve image quality of the system.

By alternating lens elements with positive and negative refractivepowers in the above-mentioned telephoto type system, the total tracklength of the optical lens system can be effectively reduced. The firstlens element provides a positive refractive power, and the aperture stopis located in front of the first lens element, so that the exit pupil ofthe optical lens system will be far away from the image plane.Therefore, the light will be projected onto the sensor with a relativelysmall incident angle, this is the telecentric feature of the image side,and this feature is very important to the photosensitive power of thecurrent solid-state sensor, and can improve the photosensitivity of thesensor while reducing the probability of the occurrence of shading. Theinflection point formed on the image-side surface of the fourth lenselement will contribute to a better correction of the incident angle ofthe off axis light with respect to the sensor. And the inflection pointformed on the object-side surface of the second lens element caneffectively correct the coma aberration caused by the system.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the image-side surface of thefirst lens element can be convex or planar or concave. If the image-sidesurface of the first lens element is convex, the first lens element is abiconvex lens element, such that the refractive power of the first lenselement can be effectively increased, and the total track length of theoptical lens system will become much shorter. If the image-side surfaceof the first lens element is planar, the first lens element is aconvex-plano lens element, it will be favorable to correct the sphericalaberration caused by the system. If the image-side surface of the firstlens element is concave, the first lens element is a meniscus lenselement, it will be favorable to correct the astigmatism caused by thesystem.

In the present optical lens system for taking image, the object-sidesurface of the fourth lens element can be convex or concave. If theobject-side surface of the fourth lens element is convex, the fourthlens element is a meniscus lens element, it will be favorable to furthercorrect various aberrations caused by the system. If the object-sidesurface of the fourth lens element is concave, the fourth lens elementis a biconcave lens element, such that the negative refractive power ofthe fourth lens element will become much larger, the principal pointwill be further far away from the image plane, and the total tracklength of the optical lens system will become much shorter.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the on-axis distance between thesecond lens element and the third lens element is T23, the focal lengthof the optical lens system for taking image is f, and they satisfy therelation:(T23/f)*100<25.

The above relation is favorable to correct the astigmatism caused by thesystem.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the lens elements can be made ofglass or plastic. If the lens elements are made of glass, there is morefreedom in distributing the refractive power of the optical lens system.If the lens elements are made of plastic, the cost will be effectivelyreduced.

In the present optical lens system for taking image, the lens elementscan be provided with aspheric surfaces, allowing more design parameters(than spherical surfaces), so as to better correct aberrations,resulting in a reduction in the number of the lens elements, and thuseffectively reducing the total track length of the optical lens system.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the focal length of the opticallens system for taking image is f, the focal length of the first lenselement and the second lens element combined is f12, and they satisfythe relation:0.98<f/f12<1.82.

If the value of f/f12 is smaller than the above lower limit, therefractive power of the system will be relatively weak, the total tracklength of the system will be longer. And if the value of f/f12 isgreater than the above upper limit, the higher order aberrations of thesystem will be too large. Further, it will be better if f/f12 satisfiesthe relation:1.28<f/f12<1.68.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the focal length of the opticallens system for taking image is f, the focal length of the first lenselement is f1, and they satisfy the relation:1.35<f/f1<2.60.

If the value of f/f1 is smaller than the above lower limit, therefractive power of the system will be relatively weak, the total tracklength of the system will be longer, and it will be difficult tosuppress the incident angle of the light with respect to the sensor; ifthe value of f/f1 is greater than the above upper limit, it will bedifficult to correct the higher order aberrations of the system.Further, it will be better if f/f1 satisfies the relation:1.55<f/f1<2.45.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the focal length of the opticallens system for taking image is f, the focal length of the third lenselement is f3, and they satisfy the relation:0.45<f/f3<0.82.

If the value of f/f3 satisfies the above relation, the refractive powerof the optical lens system can be effectively distributed and additionalhigher order aberrations will not be produced. Further, it will bebetter if f/f3 satisfies the relation:0.55<f/f3<0.75.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the focal length of the opticallens system for taking image is f, the focal length of the fourth lenselement is f4, and they satisfy the relation:0.50<|f/f4|<1.50.

If the value of |f/f4| satisfies the above relation, a balance can beobtained between the correction of aberrations and the reduction of thetotal track length. Further, it will be better if |f/f4| satisfies therelation:0.63<|f/f4|<1.20.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the focal length of the opticallens system for taking image is f, the on-axis distance between thefirst lens element and the second lens element is T12, the on-axisdistance between the second lens element and the third lens element isT23, the on-axis distance between the third lens element and the fourthlens element is T34, and they satisfy the relations:(T12/f)*100>0.4,3.5<(T34/f)*100<12.

The above relation can allow better correction of the astigmatism of thesystem.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the refractive index of the firstlens element is N1, the refractive index of the second lens element isN2, and they satisfy the relation:|N1−N2|<0.108.

The above relation can allow better correction of the astigmatism of thesystem.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the Abbe number of the first lenselement is V1, the Abbe number of the second lens element is V2, andthey satisfy the relation:|V1−V2|>23.

The above relation is favorable to correcting the chromatic aberrationcaused by the system.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the refractive index of the firstlens element is N1, the refractive index of the second lens element isN2, and they satisfy the relations:1.50<N1<1.58,1.55<N2<1.64

If N1 and N2 satisfy the above relations, it is easy to find suitableplastic material to match the optical lens system.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the focal length of the opticallens system for taking image is f, the radius of curvature of theobject-side surface of the first lens element is R1, and they satisfythe relation:0<R1/f<0.4.

The above relation can effectively improve the refractive power of thefirst lens element, such that a relatively high refractive power of theoptical lens system can be obtained, thus reducing the total tracklength of the optical lens system. Further, it will be better if R1/fsatisfies the relation:0<R1/f<0.32.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the radius of curvature of theobject-side surface of the second lens element is R3, the radius ofcurvature of the image-side surface of the second lens element is R4,and they satisfy the relation:−0.40<(R3+R4)/(R3−R4)<0.85.

The above relation can correct the Petzval sum of the system. Further,it will be better if R3 and R4 satisfy the relation:−0.35<(R3+R4)/(R3−R4)<0.5.

Further, it will be much better if R3 and R4 satisfy the relation:−0.09<(R3+R4)/(R3−R4)<0.15.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the distance from the aperturestop of the optical lens system for taking image to the image plane isDT, including a flat glass between the image-side surface of the fourthlens element and the image plane. A maximum image height of the opticallens system for taking image is ImgH, which is half of the length of thediagonal line of the effective pixel region of the electronic imagingsensor, and it satisfies the relation:

DT/ImgH<2.0. And an object to be photographed is imaged on theelectronic imaging sensor.

The above relation can maintain the objective of miniaturization of theoptical lens system for taking image. Further, it will be better ifDT/ImgH satisfies the relation:DT/ImgH<1.84.

Further, it will be much better if DT/ImgH satisfies the relation:DT/ImgH<1.78.

The present invention will become more obvious from the followingdescription when taken in connection with the accompanying drawings,which show, for purpose of illustrations only, the preferred embodimentsin accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an optical lens system for taking image in accordance witha first embodiment of the present invention;

FIG. 1B shows the aberration curves of the first embodiment of thepresent invention;

FIG. 2A shows an optical lens system for taking image in accordance witha second embodiment of the present invention;

FIG. 2B shows the aberration curves of the second embodiment of thepresent invention;

FIG. 3A shows an optical lens system for taking image in accordance witha third embodiment of the present invention;

FIG. 3B shows the aberration curves of the third embodiment of thepresent invention;

FIG. 4A shows an optical lens system for taking image in accordance witha fourth embodiment of the present invention;

FIG. 4B shows the aberration curves of the fourth embodiment of thepresent invention;

FIG. 5A shows an optical lens system for taking image in accordance witha fifth embodiment of the present invention; and

FIG. 5B shows the aberration curves of the fifth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1A, which shows an optical lens system for takingimage in accordance with a first embodiment of the present invention,and FIG. 1B shows the aberration curves of the first embodiment of thepresent invention. An optical lens system for taking image in accordancewith the first embodiment of the present invention comprises: from theobject side to the image side:

An aperture stop 50.

A plastic first lens element 10 with positive refractive power has aconvex object-side surface 11 and a convex image-side surface 12, andthe object-side surface 11 and the image-side surface 12 of the firstlens element 10 are aspheric.

A plastic second lens element 20 with negative refractive power has aconcave object-side surface 21 and a concave image-side surface 22, theobject-side surface 21 and the image-side surface 22 of the second lenselement 20 are aspheric, and inflection points are formed on theobject-side surface 21.

A plastic third lens element 30 with positive refractive power has aconcave object-side surface 31 and a convex image-side surface 32, andthe object-side surface 31 and the image-side surface 32 of the thirdlens element 30 are aspheric.

A plastic fourth lens element 40 with negative refractive power has aconvex object-side surface 41 and a concave image-side surface 42, theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40 are aspheric, and inflection points are formed on theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40.

An IR cut filter 60 is located behind the fourth lens element 40 and hasno influence on the focal length of the optical lens system.

An image plane 70 is located behind the IR cut filter 60.

The equation for the aspheric surface profiles of the first embodimentis expressed as follows:

${X(Y)} = {{\left( {Y^{2}/R} \right)/\left( {1 + {{sqrt}\left( {1 - {\left( {1 + k} \right)*\left( {Y/R} \right)^{2}}} \right)}} \right)} + {\sum\limits_{i}{({Ai})*\left( Y^{i} \right)}}}$

wherein:

X: the height of a point on the aspheric lens surface at a distance Yfrom the optical axis relative to the tangential plane at the asphericsurface vertex;

Y: the distance from the point on the curve of the aspheric surface tothe optical axis;

k: the conic coefficient;

Ai: the aspheric surface coefficient of order i.

In the first embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the focal length of the first lens element is f1, the focal length ofthe third lens element is f3, the focal length of the fourth lenselement is f4, the focal length of the first lens element and the secondlens element combined is f12, the on-axis distance between the firstlens element and the second lens element is T12, the on-axis distancebetween the second lens element and the third lens element is T23, theon-axis distance between the third lens element and the fourth lenselement is T34, and they satisfy the relations:f=6.26 mm;f/f12=1.33;f/f1=2.15;f/f3=0.70;|f/f4|=1.00;(T12/f)*100=0.8;(T23/f)*100=12.9;(T34/f)*100=10.4.

In the first embodiment of the present optical lens system for takingimage, the refractive index of the first lens element is N1, therefractive index of the second lens element is N2, and they satisfy therelations:N1=1.544;N2=1.632;|N1−N2|=0.088.

In the first embodiment of the present optical lens system for takingimage, the Abbe number of the first lens element is V1, the Abbe numberof the second lens element is V2, and they satisfy the relation:|V1−V2|=32.5.

In the first embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the radius of curvature of the object-side surface of the first lenselement is R1, the radius of curvature of the object-side surface of thesecond lens element is R3, the radius of curvature of the image-sidesurface of the second lens element is R4, and they satisfy therelations:R1/f=0.30;(R3+R4)/(R3−R4)=−0.07.

In the first embodiment of the present optical lens system for takingimage, the distance from the aperture stop of the optical lens systemfor taking image to the image plane is DT, the maximum image height ofthe optical lens system for taking image is ImgH, and they satisfy therelation:

DT/ImgH=1.77. And an object to be photographed is imaged on theelectronic imaging sensor.

The detailed optical data of the first embodiment is shown in table 1,and the aspheric surface data is shown in table 2, wherein the units ofthe radius of curvature, the thickness and the focal length areexpressed in mm, and HFOV is half of the maximal field of view.

TABLE 1 (Embodiment 1) f(focal length) = 6.26 mm, Fno = 2.85, HFOV (halfof field of view) = 31.1 deg. Curvature Focal Surface # Radius ThicknessMaterial Index Abbe # length 0 Object Plano Infinity 1 Aperture Plano−0.310 Stop 2 Lens 1  1.86996(ASP) 0.986 Plastic 1.544 55.9 2.91 3−8.38480(ASP) 0.050 4 Lens 2 −6.94910(ASP) 0.357 Plastic 1.632 23.4−5.83 5  7.99520 (ASP) 0.810 6 Lens 3 −1.79686(ASP) 1.656 Plastic 1.53055.8 9.00 7 −1.72197(ASP) 0.650 8 Lens 4 22.50670(ASP) 0.640 Plastic1.530 55.8 −6.26 9  2.86397(ASP) 0.780 10 IR-filter Plano 0.300 Glass1.517 64.2 11 Plano 0.830 12 Image Plano

TABLE 2 Aspheric Coefficients Surface # 2 3 4 5 k = −2.66615E−01−1.51624E+02 −1.14659E+02 3.75434E+01 A4 = 3.22568E−03 −4.19545E−022.34538E−02 7.33400E−02 A6 = −1.77280E−02 −1.47190E−02 −4.55841E−039.16553E−03 A8 = 1.86986E−02 3.32872E−03 7.15290E−03 −9.71964E−03 A10 =−1.62027E−02 −3.34897E−03 1.87828E−03 2.45689E−02 Surface# 6 7 8 9 k =−1.21750E+00 −8.04145E−01 −2.26437E+03 −1.18463E+01 A4 = −5.74960E−021.50268E−02 −2.20145E−02 −1.94216E−02 A6 = −1.38256E−02 −3.51815E−033.93530E−03 2.46065E−03 A8 = −4.04019E−03 8.23217E−04 −1.45084E−04−2.47010E−04 A10 = 3.34425E−03 1.11401E−04 −1.45051E−05 1.20212E−05 A12= −9.08575E−04 3.01279E−05 4.22885E−07 3.24679E−07 A14 = −2.20823E−04−2.93242E−06 1.74396E−07 −2.11767E−08 A16 = 6.81756E−05 −2.43440E−06−1.39109E−08 −1.96548E−09

Referring to FIG. 2A, which shows an optical lens system for takingimage in accordance with a second embodiment of the present invention,and FIG. 2B shows the aberration curves of the second embodiment of thepresent invention. The second embodiment of the present inventioncomprises: in order from the object side to the image side:

An aperture stop 50.

A plastic first lens element 10 with positive refractive power has aconvex object-side surface 11 and a convex image-side surface 12, andthe object-side surface 11 and the image-side surface 12 of the firstlens element 10 are aspheric.

A plastic second lens element 20 with negative refractive power has aconcave object-side surface 21 and a concave image-side surface 22, theobject-side surface 21 and the image-side surface 22 of the second lenselement 20 are aspheric, and inflection points are formed on theobject-side surface 21.

A plastic third lens element 30 with positive refractive power has aconcave object-side surface 31 and a convex image-side surface 32, andthe object-side surface 31 and the image-side surface 32 of the thirdlens element 30 are aspheric.

A plastic fourth lens element 40 with negative refractive power has aconvex object-side surface 41 and a concave image-side surface 42, theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40 are aspheric, and inflection points are formed on theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40.

An IR cut filter 60 is located behind the fourth lens element 40 and hasno influence on the focal length of the optical lens system.

An image plane 70 is located behind the IR cut filter 60.

The equation for the aspheric surface profiles of the second embodimenthas the same form as that of the first embodiment.

In the second embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the focal length of the first lens element is f1, the focal length ofthe third lens element is f3, the focal length of the fourth lenselement is f4, the focal length of the first lens element and the secondlens element combined is f12, the on-axis distance between the firstlens element and the second lens element is T12, the on-axis distancebetween the second lens element and the third lens element is T23, theon-axis distance between the third lens element and the fourth lenselement is T34, and they satisfy the relations:f=6.59 mm;f/f12=1.29;f/f1=2.32;f/f3=0.62;|f/f4|=0.84;(T12/f)*100=1.1;(T23/f)*100=15.7;(T34/f)*100=8.2.

In the second embodiment of the present optical lens system for takingimage, the refractive index of the first lens element is N1, therefractive index of the second lens element is N2, and they satisfy therelations:N1=1.544;N2=1.608;|N1−N2|=0.064.

In the second embodiment of the present optical lens system for takingimage, the Abbe number of the first lens element is V1, the Abbe numberof the second lens element is V2, and they satisfy the relation:|V1−V2|=30.3.

In the second embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the radius of curvature of the object-side surface of the first lenselement is R1, the radius of curvature of the object-side surface of thesecond lens element is R3, the radius of curvature of the image-sidesurface of the second lens element is R4, and they satisfy therelations:R1/f=0.28;(R3+R4)/(R3−R4)=0.10.

In the second embodiment of the present optical lens system for takingimage, the distance from the aperture stop of the optical lens systemfor taking image to the image plane is DT, the maximum image height ofthe optical lens system for taking image is ImgH, and they satisfy therelation:

DT/ImgH=1.82. And an object to be photographed is imaged on theelectronic imaging sensor.

The detailed optical data of the second embodiment is shown in table 3,and the aspheric surface data is shown in table 4, wherein the units ofthe radius of curvature, the thickness and the focal length areexpressed in mm, and HFOV is half of the maximal field of view.

TABLE 3 (Embodiment 2) f(focal length) = 6.59 mm, Fno = 2.85, HFOV (halfof field of view) = 30.0 deg. Curvature Focal Surface # Radius ThicknessMaterial Index Abbe # length 0 Object Plano Infinity 1 Aperture Plano−0.319 Stop 2 Lens 1  1.80904(ASP) 0.934 Plastic 1.544 55.9 2.84 3−8.71480(ASP) 0.070 4 Lens 2 −6.53810(ASP) 0.399 Plastic 1.608 25.6−4.76 5  5.31970 (ASP) 1.036 6 Lens 3 −1.95744(ASP) 1.674 Plastic 1.53055.8 10.71 7 −1.88643(ASP) 0.543 8 Lens 4 14.40200(ASP) 0.730 Plastic1.530 55.8 −7.83 9  3.16340(ASP) 0.780 10 IR-filter Plano 0.300 Glass1.517 64.2 11 Plano 0.786 12 Image Plano

TABLE 4 Aspheric Coefficients Surface # 2 3 4 5 k = −1.85763E−01−3.58739E+02 −1.70795E+02 1.47608E+01 A4 = 2.62029E−03 −2.31797E−026.60629E−03 4.95303E−02 A6 = −2.74456E−03 −1.07309E−02 −1.43853E−023.30239E−03 A8 = 6.80837E−03 2.94374E−03 1.49659E−02 −1.16095E−02 A10 =−7.98348E−03 −1.74203E−03 7.33430E−04 2.60410E−02 Surface# 6 7 8 9 k =−1.36276E+00 −7.04278E−01 −3.60327E+02 −1.26220E+01 A4 = −5.47920E−029.77416E−03 −2.15929E−02 −2.09798E−02 A6 = −1.58679E−02 −2.87642E−033.81409E−03 2.48696E−03 A8 = −5.50328E−03 6.47202E−04 −1.36033E−04−2.46666E−04 A10 = 3.54674E−03 5.31299E−05 −1.34563E−05 1.28619E−05 A12= −9.18584E−04 1.76272E−05 3.22320E−07 4.59302E−07 A14 = −2.24921E−04−2.63327E−07 1.41414E−07 −4.24480E−08 A16 = 6.81756E−05 −1.18913E−06−1.14144E−08 −2.20005E−09

Referring to FIG. 3A, which shows an optical lens system for takingimage in accordance with a third embodiment of the present invention,FIG. 3B shows the aberration curves of the third embodiment of thepresent invention. The third embodiment of the present inventioncomprises: in order from the object side to the image side:

An aperture stop 50.

A plastic first lens element 10 with positive refractive power has aconvex object-side surface 11 and a convex image-side surface 12, andthe object-side surface 11 and the image-side surface 12 of the firstlens element 10 are aspheric.

A plastic second lens element 20 with negative refractive power has aconvex object-side surface 21 and a concave image-side surface 22, andthe object-side surface 21 and the image-side surface 22 of the secondlens element 20 are aspheric.

A plastic third lens element 30 with positive refractive power has aconcave object-side surface 31 and a convex image-side surface 32, andthe object-side surface 31 and the image-side surface 32 of the thirdlens element 30 are aspheric.

A plastic fourth lens element 40 with negative refractive power has aconvex object-side surface 41 and a concave image-side surface 42, theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40 are aspheric, and inflection points are formed on theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40.

An IR cut filter 60 is located behind the fourth lens element 40 and hasno influence on the focal length of the optical lens system.

An image plane 70 is located behind the IR cut filter 60.

The equation for the aspheric surface profiles of the third embodimenthas the same form as that of the first embodiment.

In the third embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the focal length of the first lens element is f1, the focal length ofthe third lens element is f3, the focal length of the fourth lenselement is f4, the focal length of the first lens element and the secondlens element combined is f12, the on-axis distance between the firstlens element and the second lens element is T12, the on-axis distancebetween the second lens element and the third lens element is T23, theon-axis distance between the third lens element and the fourth lenselement is T34, and they satisfy the relations:f=5.93 mm;f/f12=0.96;f/f1=1.70;f/f3=1.23;|f/f4|=1.11;(T12/f)*100=1.7;(T23/f)*100=19.1;(T34/f)*100=7.1.

In the third embodiment of the present optical lens system for takingimage, the refractive index of the first lens element is N1, therefractive index of the second lens element is N2, and they satisfy therelations:N1=1.544;N2=1.632;|N1−N2|=0.088.

In the third embodiment of the present optical lens system for takingimage, the Abbe number of the first lens element is V1, the Abbe numberof the second lens element is V2, and they satisfy the relation:|V1−V2|=32.5.

In the third embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the radius of curvature of the object-side surface of the first lenselement is R1, the radius of curvature of the object-side surface of thesecond lens element is R3, the radius of curvature of the image-sidesurface of the second lens element is R4, and they satisfy therelations:R1/f=0.34;(R3+R4)/(R3−R4)=1.08.

In the third embodiment of the present optical lens system for takingimage, the distance from the aperture stop of the optical lens systemfor taking image to the image plane is DT, the maximum image height ofthe optical lens system for taking image is ImgH, and they satisfy therelation:

DT/ImgH=1.75. And an object to be photographed is imaged on theelectronic imaging sensor.

The detailed optical data of the third embodiment is shown in table 5,and the aspheric surface data is shown in table 6, wherein the units ofthe radius of curvature, the thickness and the focal length areexpressed in mm, and HFOV is half of the maximal field of view.

TABLE 5 (Embodiment 3) f(focal length) = 5.93 mm, Fno = 2.85, HFOV (halfof field of view) = 32.5 deg. Curvature Focal Surface # Radius ThicknessMaterial Index Abbe # length 0 Object Plano Infinity 1 Aperture Plano−0.270 Stop 2 Lens 1 2.02347(ASP) 0.868 Plastic 1.544 55.9 3.48 3−25.33201(ASP)  0.100 4 Lens 2 86.63811(ASP)  0.356 Plastic 1.632 23.4−6.04 5  3.64925 (ASP) 1.131 6 Lens 3 −2.28859(ASP)  1.378 Plastic 1.53055.8 4.79 7 −1.45512(ASP)  0.420 8 Lens 4 3.77664(ASP) 0.497 Plastic1.530 55.8 −5.31 9 1.53862(ASP) 0.780 10 IR-filter Plano 0.300 Glass1.517 64.2 11 Plano 1.123 12 Image Plano

TABLE 6 Aspheric Coefficients Surface # 2 3 4 5 k = −1.93392E−01−5.55828E+02 5.48578E+03 2.86059E+00 A4 = 2.30707E−03 −8.75677E−031.28975E−02 2.54139E−02 A6 = −4.88276E−03 −1.25516E−02 −1.27453E−024.54410E−03 A8 = 4.72661E−03 3.05794E−03 5.81420E−03 −1.24823E−03 A10 =−4.67879E−03 −3.91258E−03 −1.85302E−03 4.56754E−03 Surface# 6 7 8 9 k =−1.44728E+00 −7.81986E−01 −5.58153E+01 −7.05109E+00 A4 = −4.40306E−022.84899E−02 −2.10640E−02 −2.34757E−02 A6 = −5.20584E−03 −7.80416E−033.39559E−03 3.01728E−03 A8 = −5.75901E−03 2.47181E−04 −1.31038E−04−2.73458E−04 A10 = 3.20694E−04 1.38281E−04 −1.29130E−05 9.48294E−06 A12= 8.50683E−04 4.70225E−05 1.13744E−07 2.81994E−07 A14 = 5.60588E−042.90950E−06 1.15668E−07 −3.07557E−08 A16 = −5.85888E−04 −3.36770E−06−5.89772E−09 −4.28521E−10

Referring to FIG. 4A, which shows an optical lens system for takingimage in accordance with a fourth embodiment of the present invention,FIG. 4B shows the aberration curves of the fourth embodiment of thepresent invention. The fourth embodiment of the present inventioncomprises: in order from the object side to the image side:

An aperture stop 50.

A plastic first lens element 10 with positive refractive power has aconvex object-side surface 11 and a convex image-side surface 12, andthe object-side surface 11 and the image-side surface 12 of the firstlens element 10 are aspheric.

A plastic second lens element 20 with negative refractive power has aconcave object-side surface 21 and a concave image-side surface 22, theobject-side surface 21 and the image-side surface 22 of the second lenselement 20 are aspheric, and inflection points are formed on theobject-side surface 21.

A plastic third lens element 30 with positive refractive power has aconcave object-side surface 31 and a convex image-side surface 32, andthe object-side surface 31 and the image-side surface 32 of the thirdlens element 30 are aspheric.

A plastic fourth lens element 40 with negative refractive power has aconvex object-side surface 41 and a concave image-side surface 42, theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40 are aspheric, and inflection points are formed on theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40.

An IR cut filter 60 is located behind the fourth lens element 40 and hasno influence on the focal length of the optical lens system.

An image plane 70 is located behind the IR cut filter 60.

The equation for the aspheric surface profiles of the fourth embodimenthas the same form as that of the first embodiment.

In the fourth embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the focal length of the first lens element is f1, the focal length ofthe third lens element is f3, the focal length of the fourth lenselement is f4, the focal length of the first lens element and the secondlens element combined is f12, the on-axis distance between the firstlens element and the second lens element is T12, the on-axis distancebetween the second lens element and the third lens element is T23, theon-axis distance between the third lens element and the fourth lenselement is T34, and they satisfy the relations:f=6.14 mm;f/f12=1.03;f/f1=1.84;f/f3=1.07;|f/f4|=1.05;(T12/f)*100=1.2;(T23/f)*100=18.5;(T34/f)*100=8.8.

In the fourth embodiment of the present optical lens system for takingimage, the refractive index of the first lens element is N1, therefractive index of the second lens element is N2, and they satisfy therelations:N1=1.544;N2=1.632;|N1−N2|=0.088.

In the fourth embodiment of the present optical lens system for takingimage, the Abbe number of the first lens element is V1, the Abbe numberof the second lens element is V2, and they satisfy the relation:|V1−V2|=32.5.

In the fourth embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the radius of curvature of the object-side surface of the first lenselement is R1, the radius of curvature of the object-side surface of thesecond lens element is R3, the radius of curvature of the image-sidesurface of the second lens element is R4, and they satisfy therelations:R1/f=0.31;(R3+R4)/(R3−R4)=0.78.

In the fourth embodiment of the present optical lens system for takingimage, the distance from the aperture stop of the optical lens systemfor taking image to the image plane is DT, the maximum image height ofthe optical lens system for taking image is ImgH, and they satisfy therelation:

DT/ImgH=1.75. And an object to be photographed is imaged on theelectronic imaging sensor.

The detailed optical data of the fourth embodiment is shown in table 7,and the aspheric surface data is shown in table 8, wherein the units ofthe radius of curvature, the thickness and the focal length areexpressed in mm, and HFOV is half of the maximal field of view.

TABLE 7 (Embodiment 4) f(focal length) = 6.14 mm, Fno = 2.85, HFOV (halfof field of view) = 31.7 deg. Curvature Focal Surface # Radius ThicknessMaterial Index Abbe # length 0 Object Plano Infinity 1 Aperture Plano−0.324 Stop 2 Lens 1 1.91107(ASP) 0.899 Plastic 1.544 55.9 3.33 3−29.45970(ASP)  0.073 4 Lens 2 −32.82630(ASP)  0.365 Plastic 1.632 23.4−5.69 5  4.05720 (ASP) 1.138 6 Lens 3 −2.11102(ASP)  1.354 Plastic 1.53055.8 5.71 7 −1.51931(ASP)  0.540 8 Lens 4 5.12240(ASP) 0.523 Plastic1.530 55.8 −5.85 9 1.86351(ASP) 0.780 10 IR-filter Plano 0.300 Glass1.517 64.2 11 Plano 1.032 12 Image Plano

TABLE 8 Aspheric Coefficients Surface # 2 3 4 5 k = −9.12349E−02−1.07552E+04 −1.59296E+04 4.10612E+00 A4 = 3.36879E−03 −8.48082E−037.84874E−03 2.93045E−02 A6 = −6.02694E−05 −9.08945E−03 −1.24808E−024.33748E−03 A8 = 2.12558E−03 5.57279E−03 8.58581E−03 −5.64936E−03 A10 =−2.50251E−03 −5.21655E−03 −3.02370E−03 1.07016E−02 Surface# 6 7 8 9 k =−1.69217E+00 −7.34531E−01 −1.19382E+02 −9.26066E+00 A4 = −5.14203E−021.85378E−02 −2.55418E−02 −2.37298E−02 A6 = −1.61437E−02 −5.49788E−033.88293E−03 2.48234E−03 A8 = 2.83906E−04 1.37876E−04 −8.80418E−05−1.98307E−04 A10 = 7.72158E−04 9.89693E−05 −1.42986E−05 9.87774E−06 A12= −8.85615E−04 6.08222E−05 −4.16478E−07 1.23240E−07 A14 = −2.13268E−046.95766E−06 8.13481E−08 −4.01450E−08 A16 = 6.08573E−05 −3.81889E−06−1.59776E−09 −1.07759E−09

Referring to FIG. 5A, which shows an optical lens system for takingimage in accordance with a fifth embodiment of the present invention,FIG. 5B shows the aberration curves of the fifth embodiment of thepresent invention. The fifth embodiment of the present inventioncomprises: in order from the object side to the image side:

An aperture stop 50.

A plastic first lens element 10 with positive refractive power has aconvex object-side surface 11 and a convex image-side surface 12, andthe object-side surface 11 and the image-side surface 12 of the firstlens element 10 are aspheric.

A plastic second lens element 20 with negative refractive power has aconcave object-side surface 21 and a concave image-side surface 22, theobject-side surface 21 and the image-side surface 22 of the second lenselement 20 are aspheric, and inflection points are formed on theobject-side surface 21.

A plastic third lens element 30 with positive refractive power has aconcave object-side surface 31 and a convex image-side surface 32, andthe object-side surface 31 and the image-side surface 32 of the thirdlens element 30 are aspheric.

A plastic fourth lens element 40 with negative refractive power has aconcave object-side surface 41 and a concave image-side surface 42, theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40 are aspheric, and inflection points are formed on theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40.

An IR cut filter 60 is located behind the fourth lens element 40 and hasno influence on the focal length of the optical lens system.

An image plane 70 is located behind the IR cut filter 60.

The equation for the aspheric surface profiles of the fifth embodimenthas the same form as that of the first embodiment.

In the fifth embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the focal length of the first lens element is f1, the focal length ofthe third lens element is f3, the focal length of the fourth lenselement is f4, the focal length of the first lens element and the secondlens element combined is f12, the on-axis distance between the firstlens element and the second lens element is T12, the on-axis distancebetween the second lens element and the third lens element is T23, theon-axis distance between the third lens element and the fourth lenselement is T34, and they satisfy the relations:f=6.28 mm;f/f12=1.33;f/f1=2.24;f/f3=0.81;|f/f4|=1.17;(T12/f)*100=0.8;(T23/f)*100=12.8;(T34/f)*100=9.5.

In the fifth embodiment of the present optical lens system for takingimage, the refractive index of the first lens element is N1, therefractive index of the second lens element is N2, and they satisfy therelations:N1=1.544;N2=1.621;|N1−N2|=0.077.

In the fifth embodiment of the present optical lens system for takingimage, the Abbe number of the first lens element is V1, the Abbe numberof the second lens element is V2, and they satisfy the relation:|V1−V2|=31.5.

In the fifth embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the radius of curvature of the object-side surface of the first lenselement is R1, the radius of curvature of the object-side surface of thesecond lens element is R3, the radius of curvature of the image-sidesurface of the second lens element is R4, and they satisfy therelations:R1/f=0.30;(R3+R4)/(R3−R4)=−0.29.

In the fifth embodiment of the present optical lens system for takingimage, the distance from the aperture stop of the optical lens systemfor taking image to the image plane is DT, the maximum image height ofthe optical lens system for taking image is ImgH, and they satisfy therelation:

DT/ImgH=1.77. And an object to be photographed is imaged on theelectronic imaging sensor.

The detailed optical data of the fifth embodiment is shown in table 9,and the aspheric surface data is shown in table 10, wherein the units ofthe radius of curvature, the thickness and the focal length areexpressed in mm, and HFOV is half of the maximal field of view

TABLE 9 (Embodiment 5) f(focal length) = 6.28 mm, Fno =2.85, HFOV (halfof field of view) = 31.2 deg. Curvature Focal Surface # Radius ThicknessMaterial Index Abbe # length 0 Object Plano Infinity 1 Aperture Plano−0.308 Stop 2 Lens 1  1.89760(ASP) 1.006 Plastic 1.544 55.9 2.81 3−6.36710(ASP) 0.050 4 Lens 2 −5.18510(ASP) 0.376 Plastic 1.621 24.4−5.33 5  9.39710 (ASP) 0.804 6 Lens 3 −1.88781(ASP) 1.568 Plastic 1.54455.9 7.70 7 −1.68263(ASP) 0.596 8 Lens 4 −10.22590(ASP)  0.831 Plastic1.530 55.8 −5.35 9  4.02830(ASP) 1.200 10 IR-filter Plano 0.300 Glass1.517 64.2 11 Plano 0.322 12 Image Plano

TABLE 10 Aspheric Coefficients Surface # 2 3 4 5 k = −2.63432E−01−1.26356E+02 −8.31854E+01 3.81373E+01 A4 = 2.87296E−03 −4.05955E−022.00227E−02 7.71390E−02 A6 = −1.61869E−02 −1.57366E−02 −8.54150E−034.07638E−03 A8 = 1.80880E−02 1.91887E−03 4.17556E−03 −8.38807E−03 A10 =−1.54412E−02 −2.05296E−03 3.85904E−03 2.25277E−02 Surface# 6 7 8 9 k =−1.22189E+00 −8.08541E−01 −2.67330E+01 −1.74675E+01 A4 = −5.65320E−021.45001E−02 −2.01101E−02 −1.99713E−02 A6 = −8.24281E−03 −3.34731E−033.93000E−03 2.45348E−03 A8 = −3.54986E−03 9.79183E−04 −1.56921E−04−2.61699E−04 A10 = 2.69981E−03 1.59425E−04 −1.64668E−05 1.18161E−05 A12= −4.71782E−04 3.42930E−05 5.97365E−07 3.23051E−07 A14 = −2.35259E−05−4.78806E−06 1.97774E−07 −1.15837E−08 A16 = 1.45228E−04 −3.13716E−06−2.31158E−08 −2.79801E−09

TABLE 11 Embodi- Embodi- Embodi- Embodi- Embodi- ment 1 ment 2 ment 3ment 4 ment 5 f 6.26 6.59 5.93 6.14 6.28 Fno 2.85 2.85 2.85 2.85 2.85HFOV 31.1 30.0 32.5 31.7 31.2 N1 1.544 1.544 1.544 1.544 1.544 N2 1.6321.608 1.632 1.632 1.621 | N1 − N2 | 0.088 0.064 0.088 0.088 0.077 | V1 −V2 | 32.5 30.3 32.5 32.5 31.5 f/f12 1.33 1.29 0.96 1.03 1.33 f/f1 2.152.32 1.70 1.84 2.24 f/f3 0.70 0.62 1.23 1.07 0.81 | f/f4 | 1.00 0.841.11 1.05 1.17 (T12/f)*100 0.8 1.1 1.7 1.2 0.8 (T23/f)*100 12.9 15.719.1 18.5 12.8 (T34/f)*100 10.4 8.2 7.1 8.8 9.5 R1/f 0.30 0.28 0.34 0.310.30 (R3 + R4)/ −0.07 0.10 1.08 0.78 −0.29 (R3 − R4) DT/ImgH 1.77 1.821.75 1.75 1.77

In the present optical lens system for taking image, the lens elementscan be made of glass or plastic. If the lens elements are made of glass,there is more freedom in distributing the refractive power of theoptical lens system. If the lens elements are made of plastic, the costwill be effectively reduced.

It is to be noted that the tables 1-10 show different data from thedifferent embodiments, however, the data of the different embodiments isobtained from experiments. Therefore, any product of the same structureis deemed to be within the scope of the present invention even if ituses different data. Table 11 lists the relevant data for the variousembodiments of the present invention.

While we have shown and described various embodiments in accordance withthe present invention, it should be clear to those skilled in the artthat further embodiments may be made without departing from the scope ofthe present invention.

1. An optical lens system for taking image comprising, in order from theobject side to the image side: an aperture stop; a first lens elementwith positive refractive power having a convex object-side surface; aplastic second lens element with negative refractive power having aconcave object-side surface and a concave image-side surface, theobject-side and the image-side surfaces of the second lens element beingaspheric; a third lens element with positive refractive power having aconcave object-side surface and a convex image-side surface; a fourthlens element with negative refractive power having a convex object-sidesurface and a concave image-side surface; and in the optical lens systemfor taking image, the number of lens elements with refractive powerbeing limited to four; wherein a radius of curvature of the object-sidesurface of the second lens element is R3, a radius of curvature of theimage-side surface of the second lens element is R4, they satisfy therelation:−0.40<(R3+R4)/(R3−R4)<0.85.
 2. The optical lens system for taking imageas claimed in claim 1, wherein the third lens element is made of plasticmaterial, the object-side surface and the image-side surface of thethird lens element are aspheric, the fourth lens element is made ofplastic material, the object-side surface and the image-side surface ofthe fourth lens element are aspheric, and inflection points are formedon the fourth lens element.
 3. The optical lens system for taking imageas claimed in claim 2, wherein an image-side surface of the first lenselement is convex, a focal length of the optical lens system for takingimage is f, an on-axis distance between the first lens element and thesecond lens element is T12, an on-axis distance between the second lenselement and the third lens element is T23, and they satisfy therelations:(T12/0*100>0.4,0.4<(T23/f)*100<25.
 4. The optical lens system for taking image as claimedin claim 3, wherein the radius of curvature of the object-side surfaceof the second lens element is R3, the radius of curvature of theimage-side surface of the second lens element is R4, they satisfy therelation:−0.35<(R3+R4)/(R3−R4)<0.50.
 5. The optical lens system for taking imageas claimed in claim 4, wherein the radius of curvature of theobject-side surface of the second lens element is R3, the radius ofcurvature of the image-side surface of the second lens element is R4,they satisfy the relation:−0.09<(R3+R4)/(R3−R4)<0.15.
 6. The optical lens system for taking imageas claimed in claim 2, wherein the first lens element is made of plasticmaterial, the object-side surface and an image-side surface of the firstlens element are aspheric, inflection points are formed on theobject-side surface of the second lens element, a focal length of theoptical lens system for taking image is f, an on-axis distance betweenthe third lens element and the fourth lens element is T34, and theysatisfy the relation:3.5<(T34/f)*100<12.
 7. The optical lens system for taking image asclaimed in claim 2, wherein a distance from the aperture stop of theoptical lens system for taking image to an image plane is DT, a maximumimage height of the optical lens system for taking image is ImgH, theysatisfy the relation:DT/ImgH<2.0, and an object to be photographed is imaged on an electronicimaging sensor.
 8. The optical lens system for taking image as claimedin claim 1, wherein a refractive index of the first lens element is N1,a refractive index of the second lens element is N2, they satisfy therelation:|N1−N2|<0.108, an Abbe number of the first lens element is V1, an Abbenumber of the second lens element is V2, and they satisfy the relation:|V1−V2|>23.
 9. The optical lens system for taking image as claimed inclaim 1, wherein a focal length of the optical lens system for takingimage is f, a radius of curvature of the object-side surface of thefirst lens element is R1, and they satisfy the relation:0<R1/f<0.4.
 10. The optical lens system for taking image as claimed inclaim 9, wherein the focal length of the optical lens system for takingimage is f, the radius of curvature of the object-side surface of thefirst lens element is R1, and they satisfy the relation:0<R1/f<0.32.
 11. The optical lens system for taking image as claimed inclaim 1, wherein a refractive index of the second lens element is N2,and it satisfies the relation:1.55<N2<1.64.